Pipe construction system

ABSTRACT

A pipe construction system which utilises a multiplicity of arcuate pipe segments  11, 12  to form a pipe section  10  and which sections are assembled together to form a length of pipe. Each segment  11, 12  has two longitudinal edges  13  of increased radial thickness and having a groove  14  formed in the circumferential direction whereby an interlocking and sealing member  15  may be located in the aligned grooves  14  of two adjacent segments  11, 12.  One end of a pipe section  10  assembled from the segments defines a socket  22  for receiving a spigot  23  defined at the other end of a like section. The spigot end of each segment has a pocket  25  formed along said edge  13  but within the thickness of the major area of the segment, which pocket  25  mates with a corresponding pocket  25  of an adjacent segment whereby sealant may be disposed in the mating pockets.

[0001] This invention relates to a pipe construction system and also toa method for constructing a pipe from a multiplicity of pipe segments.Certain aspects of this invention concern the lining of an undergroundsewer, using the pipe construction system.

[0002] In the following description and explanation of this invention,reference will be made primarily to the lining of underground sewers,though it is to be understood that the pipe construction system of thisinvention is not limited to this application, and may be used for a verywide range of different applications. For example, the system may beused to construct an overland or underground pipe, as well as to line awide variety of ducts, so long as the duct is sufficiently large topermit access by human operators, to effect the lining method.

[0003] Many underground sewers in major cities throughout the world wereconstructed more than 100 years ago. Consequently, those sewers are bynow becoming very worn internally, with the brickwork or otherconstructional materials deteriorating in view of the nature of theliquids and gases present within the sewer. Further, due to groundmovements over the years, the structural integrity of those sewers canbe seriously compromised. These aspects can lead to failure withinsewers, by the walls of the sewers collapsing inwardly. The consequentremedial work necessary to restore the sewer is extremely difficult andunpleasant to perform, since by the time such work is commenced, thereis likely to be a large volume of sewage backed up behind a blockagecaused by the failure.

[0004] It is known to provide a lining within underground ducts such assewers, in an attempt to restore integrity to the structure. Such alining technique may be performed before there is a catastrophicfailure, by opening the sewer at a convenient point and then fittinginto the sewer relatively short lengths of pipe which are connectedtogether end-to-end. In the case of a sewer of circular cross-sectionalshape, such short lengths of a pipe may be a sliding fit within theexisting sewer so that no further work is required. Alternatively, theexternal diameter of the assembled pipe may be significantly less thanthe internal diameter of the sewer and then a grouting material isinjected under pressure into the generally annular space between thepipe and the internal sewer wall.

[0005] Particularly in the case of relatively large sewers, it is alsoknown to assemble a lining from short lengths of pipe which lengthsthemselves are assembled from segments each of part-circular shape. Onewidely used system employs a tongue along one axially-extending edge ofa segment and a correspondingly formed groove along the otheraxially-extending edge of a segment whereby the segments may beassembled together with the tongue of one segment fitting into thegroove of the next adjacent segment. This system has the disadvantagethat the strength of the segments is much reduced in the area of theinter-fitting tongues and grooves resulting in a relatively weak jointbetween adjacent segments. Further, it is necessary axially to slide thelast segment (or the second segment, where two semi-circular segmentsform the pipe section) into position and during this sliding movement,there is a relatively high risk that the tongue or one of the groovewalls will be broken away from its segment.

[0006] An alternative but similar system uses butt or halved jointsbetween adjacent lining segments, each of which joints is reinforcedwith an elongate internal cover plate secured over the joint. Such asystem is slow and inconvenient to install, especially within theconfined working space of a sewer.

[0007] A disadvantage of the above systems is that the strength andwater-tight integrity of a pipe assembled as described is relatively lowand so the systems are unsuitable for use other than in a groutedpipe-lining situation, where the strength may be enhanced by thesurrounding grout and already existing duct or sewer. Even so, the jointcould still leak and over a period of time and so deteriorate theintegrity of the surrounding grout.

[0008] It has been proposed to strengthen the longitudinal jointsbetween adjacent segments by enlarging the wall thickness in the regionof the joints but in order to give a smooth internal surface to thefinished pipe, all such enlargement must be effected externally of thepipe. However, this then gives rise to a problem at the ends of the pipesections where the end of one pipe section forms a spigot which fitsinto a socket formed at the opposite end of the next adjacent pipesection. The enlarged wall thickness must be cut away and this leads toa very weak area of the assembled pipe, which also is highly likely toleak.

[0009] The present invention has as a principal object the provision ofa pipe construction system which at least mitigates the disadvantages ofthe known form of segmented lining systems as discussed above, and sowhich may be used not only for pipe lining, but also to construct pipelines in general, for use either above or below ground, as may berequired.

[0010] Accordingly, one aspect of the present invention provides a pipeconstruction system comprising: a multiplicity of arcuate pipe segmentsa plurality of which may be assembled together to form a pipe sectionwhich defines at one end a socket for receiving a spigot defined at theother end of a like section also assembled from a plurality of saidsegments whereby a length of pipe may be built up from the assembledsections, each segment having two edge regions parallel to the length ofthe pipe section each of which edge regions is of increased radialthickness and is formed with a groove extending from the socket end upto the spigot-forming end of the segment, and at the spigot forming endof a segment there is formed a pocket along said edge but within thethickness of the major area of the segment which pocket mates with acorresponding pocket of the adjacent segment whereby a sealant may bedisposed in the mating pockets.

[0011] It will be appreciated that with the pipe construction system ofthis invention, the formation at both axially-extending edges of eachsegment should be essentially the same. By providing the edge regionswith an increased radial thickness, that formation may be madesufficiently strong and certainly no weaker than the strength of themajor area of the segment and thus the likelihood of damage to thoseformations is greatly reduced, both during handling of a segment priorto assembly to form a pipe section within a sewer, and as the segment isassembled into a pipe section. Subsequent to the assembly of thesegments into a pipe section, a setting or curing sealant compound maybe injected into the mating grooves, thereby to effect a seal betweenthe segments and also to lock together the segments, once the compoundhas set or cured, as appropriate.

[0012] Preferably, each said groove is of re-entrant form whereby thecompound, once cured or set, is mechanically held in the two alignedgrooves. One preferred form of groove is of dovetail cross-sectionalshape, whereby the cured or set compound forms a mechanical interlockingmember of a corresponding profile, in effect having two dovetailportions with the narrower ends thereof joined together. The compoundalso performs the sealing function as discussed above.

[0013] Curing or setting compounds can be made from a suitable resinsystem which may be reinforced with fibre strands and fillers, thesystem ensuring that a homogeneous composite structure is formedfollowing the casting of the bonding interlocking member.

[0014] The pockets along said edges of each segment must open throughthe respective edge itself, in order that the pocket may mate with thepocket of the next adjacent segment to be assembled thereto. In theevent that each such pocket also opens through the end face of thesegment, the sealant may be injected into the mating pockets through theend face openings thereof. Alternatively, where each pocket is closedexcept for its opening through the axial edge of the segment, sealantmay be injected into the mating pockets by drilling a hole into themating pockets either from within the assembled pipe section or fromoutside (depending upon the intended use of the assembled pipe) and thenthe sealant injected through that drilled hole.

[0015] Each pocket preferably extends in the axial direction either fromthe adjacent end face of the segment or a position closely spacedtherefrom, towards the other end of the segment for a sufficientdistance such that the pocket terminates in the general region of theincreased thickness part of the segment. The sealant does not need tohave a high strength since the encircling part of the socket of the nextadjacent pipe section will confer sufficient strength on the assembly.Thus, the sealant may be in the form of a conventional mastic.

[0016] In one possible system of this invention, the groove on eachaxially extending edge of a segment is defined by a pre-formed componentbonded to the respective edge of a segment during the manufacturethereof. Such a preformed component may comprise a plastics materialmoulding, reinforced as appropriate with fibres or the like extendingalong the length of the component. The major part of each segment mayalso comprise a fibre-reinforced plastics material moulding such as ofglass-reinforced plastics material. In an alternative construction, themajor part of each segment has inner and outer skins each of a glassreinforced plastics material and a filled plastics material (such as asand-filled plastics resin) being disposed between the skins.

[0017] In order to enhance the integrity of the longitudinal jointbetween two segments, a reinforcing strip may be laid over the joint,either externally, internally, or both externally and internally, at thetime of assembling the segments together. Conveniently, such a strip issecured to one segment to run along but project from the longitudinaledge of the segment, before assembly of that segment to another. Then,when assembled to the other segment, the strip is also secured to theother segment, to cover the joint. The strip could be clamped in placefor example using mechanical fasteners such as screws, perhaps with aclamping bar, or could be bonded using a suitable adhesive.

[0018] The reinforcing strip may be of a fibre-reinforced plasticsmaterial, and is advantageously fitted before the casting of theinterlocking member. In this case, the strip may ensure that during theinterlocking member casting step the sealant material is containedmostly within the interlocking grooves, and so does not escape fromthese grooves to any substantial extent. Also, following completion, thestrip will add further strength and reinforcement to the longitudinaljoint.

[0019] During assembly of the pipe from the sections, a suitable mastic,other sealant or a gasket may be applied to the complete socket beforethe next section to be assembled is fitted thereto, again to conferwater-tightness to the completed pipe.

[0020] According to a second aspect of this invention, there is provideda method of constructing a pipe from a multiplicity of arcuate pipesegments a plurality of which may be assembled together to form a pipesection which defines at one end a socket for receiving a spigot definedat the other end of a like section also assembled from a plurality ofthe segments whereby a length of the pipe may be built up from theassembled sections, each segment having two edge regions parallel to thelength of the pipe section each of which edge regions is of increasedradial thickness and is formed with a groove extending from the socketend up to the spigot-forming end of the segment; and at the spigotforming end of a segment there is formed a pocket along said edge butwithin the thickness of the major area of the segment which pocket mateswith a corresponding pocket of the adjacent segment; in which method:

[0021] a pipe section is assembled from a plurality of the segments byaligning said grooves along adjacent segment edges;

[0022] a setting or curing sealant compound is injected into each pairof aligned grooves and is allowed to set or cure to provide a bondinginterlocking member;

[0023] a sealing agent is furnished in the mating pockets at the spigotend of the section;

[0024] a further section is assembled in a like manner;

[0025] sealant is disposed at least one of internally around the socketof one section or externally around the spigot of the other section; and

[0026] the socket of one section and the spigot of the other section areinterengaged.

[0027] According to a further but closely related method of constructinga pipe from a multiplicity of arcuate pipe segments a plurality of whichmay be assembled together to form a pipe section which defines at oneend a socket for receiving a spigot defined at the other end of a likesection also assembled from a plurality of the segments whereby a lengthof the pipe may be built up from the assembled sections, each segmenthaving two edge regions parallel to the length of the pipe section eachof which edge regions is of increased radial thickness and is formedwith a groove extending from the socket end up to the spigot-forming endof the segment; and at the spigot forming end of a segment there isformed a pocket along said edge but within the thickness of the majorarea of the segment which pocket mates with a corresponding pocket ofthe adjacent segment; in which method:

[0028] a pipe section is assembled from a plurality of the segments byaligning said grooves along adjacent segment edges;

[0029] a setting or curing sealant compound is injected into each pairof aligned grooves, and is allowed to set or cure to provide a bondinginterlocking member;

[0030] a sealing agent is furnished in the mating pockets at the spigotend of the section;

[0031] sealant is disposed either internally around the socket of thesection or externally around the spigot thereof;

[0032] the segments of a further section are fitted into the socket oraround the spigot of the already assembled section, to assemble afurther section in a like manner but coupled to the already assembledsection; and then

[0033] a setting or curing sealant compound is injected into each pairof aligned grooves of the further section, and is allowed to set orcure; and

[0034] a sealing agent is furnished in the mating pockets at the spigotend of the section.

[0035] According to yet another aspect of this invention, there isprovided a method of lining an existing closed duct comprising effectingwithin that existing closed duct a pipe construction method of thisinvention as described above so as to build up the pipe in situ in theduct but with clearance between the outer wall of the pipe and the innerwall of the duct, and then filling that clearance with a groutingmaterial.

[0036] By way of example only, one specific embodiment of a pipeconstruction system of this invention will now be described in detail,reference being made to accompanying drawings, in which:—

[0037]FIG. 1 is a diagrammatic side view of a section of a pipe made upfrom a pipe construction system of this invention, using twosemi-circular segments to make up the section;

[0038]FIG. 2 is a cross-section through the pipe of FIG. 1;

[0039]FIGS. 3 and 4 are detailed cross-sections on an enlarged scale,through the pipe section of FIG. 1, taken on lines II-II and III-IIImarked on that Figure; and

[0040]FIG. 5 is a further cross-section through the joint betweenadjacent long edges of two segments, showing additional details.

[0041] The embodiment of pipe construction system shown in the drawingsis intended for lining an already existing underground sewer having atypical diameter in the range of 800 mm to perhaps 2500 mm or more.Though a circular pipe is shown, for use with a sewer of circularcross-sectional shape, the system may be manufactured to have othercross-sectional shapes to suit a sewer being lined—for example, manysewers are of egg-shaped cross-section and the segments making up eachsection of the pipe may be suitably profiled so that the assembledsection has a corresponding cross-section.

[0042] In FIGS. 1 and 2, the section 10 of a pipe is shown assembledfrom two segments 11, 12, each of semi-circular cross-sectional shape,whereby the assembled section is of circular cross-section. Eachlongitudinally-extending edge 13 of each segment has an enlargedthickness and defines a groove 14 of dovetail cross-sectional shape. Thealigned adjacent edges 13 of the segments are connected together bymeans of an interlock member 15 cast in-situ in the grooves, byinjecting into those grooves a setting or curing sealant component suchas an epoxy resin compound. The interlock member thus has a doubledovetail form, with the narrower ends of the two dovetails joinedtogether, as shown in FIGS. 3 and 5.

[0043] Each groove 14 is defined by a pre-formed component 17, providedalong the respective longitudinal edge 13 of each segment 11, 12, duringthe manufacture of that segment. The component 17 may, for example, bemade from a glass fibre reinforced plastics material. Then, the majorpart of each segment may be moulded to two components 17, that majorpart being made up from inner and outer glass fibre reinforced plasticsskins 18, 19, with a core 20 of a resin/aggregate mix. The two skins mayuse unidirectional E-glass fibre stitch-bonded to chopped strand matembedded in a polyester resin and arranged so as to give the maximumhoop-strength to the finished segment.

[0044] As shown in FIG. 1, one end of each segment 11, 12 is profiled toprovide a part of a socket 22 so that when the two segments areassembled, a complete socket is formed around one end of the section.The internal diameter of that socket should be slightly greater than theouter diameter of the section, ignoring the region of increasedthickness along the long edges 13. At the other end of the segment, theregion of increased thickness is cut away, so that the outer surface ofthe completed section is circular, as indicated at 23, to form a spigotwhich may be received in a socket of the next adjacent pipe section,during assembly.

[0045] Within the spigot region of each segment, and opening into bothlong edges of the segment are two pockets 25. As shown in FIG. 1, thosepockets extend from the radial end face 26 at the spigot along thelength of the segment and slightly overlap the region of increasedthickness. Thus, when the two segments are connected together as shownin FIG. 1, the respective pairs of pockets 25 mate to provide a singlepocket within the thickness of the adjoining segments. This singlepocket is, during assembly, filled with a mastic sealant, in order toimpart water-tightness to this region of the assembled pipe section.

[0046] The pipe is assembled in a sewer to form an internal lining bycarrying the segments along a sewer from an access point and thenmanoeuvring into position the segments, two at a time to form completelining sections. Each section is completed by injecting a setting orcuring sealant compound into the aligned grooves 14 of adjacent edges 13to cast in-situ the interlock member 15 to complete a joint betweenthose edges. Conveniently, the injection is achieved by vacuum drawingthe compound along the length of the aligned grooves, for example byconnecting a vacuum pump at one end of those grooves and injecting thecompound from the other end. During this process, the compound alsotends to flow between the adjoining edges 27 (FIG. 3) thereby to give avery strong and water-tight joint.

[0047] Mastic is injected into the mating pockets 25 from the radial endface 26, to complete the seal between the segments, in this region. Oncecompleted, the assembled section is pushed axially fully to engage thespigot portion 23 with the socket 22 of a previously assembled section.A sealant, sealing member or a gasket may be provided within the socket22 following the completion of a section, so that on pressing thereduced diameter portion of the next section into the socket, awater-tight seal between the two pipe sections is formed.

[0048] Finally, a grouting material such as a cement-based grout isinjected into the space between the internal wall of the existing sewerand the external surface of the assembled section, so integrating thesection with the existing sewer. Preferably, the section isapproximately centred within the sewer. This may be achieved by wedgingthe section as appropriate during assembly.

[0049] An alternative assembly technique may be appropriate for theconstruction of a sewer lining from pipe sections each having only twosegments, as shown in the drawings. Following the completion of one pipesection, with the socket end exposed for the connection thereto of thenext section, a suitable mastic or gasket is applied around the internalsurface of that socket. Then, a pipe segment is fitted into that socket,whereafter the second pipe segment (which completes the next pipesection) is also fitted into that socket with its edges in alignmentwith the already positioned segment. To permit the setting or curingsealant compound to be injected into the grooves, holes may be drilledinto the grooves from the end of the pipe section adjacent the socket ofthe previously assembled section, the compound then being injected intothose holes whilst a vacuum is drawn from the exposed other ends of thegrooves. Mastic may be injected into the mating pockets at the spigotend, which pockets lie mostly within the confines of the socket of thepreviously assembled pipe section, by drilling holes into the pocketsfrom within the pipe section and injecting the mastic through thoseholes.

[0050]FIG. 5 is a cross-section through the enlarged thicknesslongitudinal joint, including the cast in-situ interlocking member 15.Also shown in this figure is an optional reinforcing strip 30 whichoverlaps the longitudinal joint, externally of the two segments. Thisstrip is made of a fibre-reinforced plastics sheet material and isbonded initially to one segment by a suitable adhesive so as to projectfrom the longitudinal edge thereof. Then, during assembly, the strip 30is bonded to the other segment, before the in-situ casting of theinterlocking member 15.

[0051] In addition to reinforcing the strength and integrity of the pipesection, the strip has the additional function of assisting containingthe compound in the grooves 14 during the injection thereof. Thisfunction may be enhanced if a corresponding strip is fitted to theinternal surfaces of the segments, as well (not shown).

1. A pipe construction system comprising a multiplicity of arcuate pipesegments a plurality of which may be assembled together to form a pipesection which defines at one end a socket for receiving a spigot definedat the other end of a like section also assembled from a plurality ofsaid segments whereby a length of pipe may be built up from theassembled sections, each segment having two edge regions parallel to thelength of the pipe section each of which edge regions is of increasedradial thickness and is formed with a groove extending from the socketend up to the spigot-forming end of the segment, and at the spigotforming end of a segment there is formed a pocket along said edge butwithin the thickness of the major area of the segment which pocket mateswith a corresponding pocket of the adjacent segment whereby a sealantmay be disposed in the mating pockets.
 2. A pipe construction system asclaimed in claim 1, wherein each said groove is of re-entrant formwhereby an interlocking member maybe cast in-situ in the aligned groovesof adjacent section edges, mechanically to hold those edges together. 3.An internal lining as claimed in claim 2, wherein each groove is ofdovetail form, in cross-section.
 4. A pipe construction system asclaimed in any of the preceding claims, wherein the edge region ofincreased radial thickness and defining said groove comprises apre-formed component bonded to the material of the major part of thesegment during the manufacture thereof.
 5. A pipe construction system asclaimed in claim 4, wherein the major part of each segment comprises afibre-reinforced plastics material moulding.
 6. A pipe constructionsystem as claimed in claim 4, wherein the major part of each segmentcomprises inner and outer skins of a fibre-reinforced plastics materialbetween which is disposed a resin-impregnated filler.
 7. An internallining system as claimed in any of the preceding claims, wherein areinforcing strip extends along and projects from the longitudinal edgeregion of one segment, for bonding to the corresponding edge region ofanother segment with which said one segment is assembled.
 8. A method ofconstructing a pipe from a multiplicity of arcuate pipe segments aplurality of which may be assembled together to form a pipe sectionwhich defines at one end a socket for receiving a spigot defined at theother end of a like section also assembled from a plurality of thesegments whereby a length of the pipe may be built up from the assembledsections, each segment having two edge regions parallel to the length ofthe pipe section each of which edge regions is of increased radialthickness and is formed with a groove extending from the socket end upto the spigot-forming end of the segment; and at the spigot forming endof a segment there is formed a pocket along said edge but within thethickness of the major area of the segment which pocket mates with acorresponding pocket of the adjacent segment; in which method: a pipesection is assembled from a plurality of the segments by aligning saidgrooves along adjacent segment edges; a setting or curing sealantcompound is injected into each pair of aligned grooves and is allowed toset or cure to provide a bonding interlocking member; a sealing agent isfurnished in the mating pockets at the spigot end of the section; afurther section is assembled in a like manner; sealant is disposed atleast one of internally around the socket of one section or externallyaround the spigot of the other section; and the socket of one sectionand the spigot of the other section are interengaged.
 9. A method asclaimed in claim 8, in which the setting or curing sealant compound isinjected into the aligned grooves by drawing a vacuum from the groovesfrom one end of the section whilst injecting the compound into thegrooves from the other end of the section.
 10. A method as claimed inclaim 9, in which said setting or curing sealant compound is permittedto flow between the interfacing edges of the respective segments.
 11. Amethod as claimed in any of claims 8 to 10, in which the pockets openinto the radial end face of the section and a sealing agent is injectedinto those pockets from said end face.
 12. A method as claimed in any ofclaims 8 to 11, in which said sealing agent comprises a non-settingmastic.
 13. A method as claimed in any of claims 8 to 12, in which saidsealant comprises a sealing gasket fitted either around the spigot orinternally within the socket.
 14. A method as claimed in any of claims 8to 13, wherein a reinforcing strip is secured to at least one of theinternal and external adjacent edge regions of two segments to bridgethe longitudinal joint.
 15. A method of constructing a pipe from amultiplicity of arcuate pipe segments a plurality of which may beassembled together to form a pipe section which defines at one end asocket for receiving a spigot defined at the other end of a like sectionalso assembled from a plurality of the segments whereby a length of thepipe may be built up from the assembled sections, each segment havingtwo edge regions parallel to the length of the pipe section each ofwhich edge regions is of increased radial thickness and is formed with agroove extending from the socket end up to the spigot-forming end of thesegment; and at the spigot forming end of a segment there is formed apocket along said edge but within the thickness of the major area of thesegment which pocket mates with a corresponding pocket of the adjacentsegment; in which method: a pipe section is assembled from a pluralityof the segments by aligning said grooves along adjacent segment edges; asetting or curing sealant compound is injected into each pair of alignedgrooves, and is allowed to set or cure to provide a bonding interlockingmember; a sealing agent is furnished in the mating pockets at the spigotend of the section; sealant is disposed either internally around thesocket of the section or externally around the spigot thereof; thesegments of a further section are fitted into the socket or around thespigot of the already assembled section, to assemble a further sectionin a like manner but coupled to the already assembled section; and thena setting or curing sealant compound is injected into each pair ofaligned grooves of the further section, and is allowed to set or cure;and a sealing agent is furnished in the mating pockets at the spigot endof the section.
 16. A method as claimed in claim 15, in which thesetting or curing compound is injected into the grooves of each furthersection by forming an opening into the grooves from internally withinthe further section adjacent the previously-assembled section, and thendrawing a vacuum from the grooves through said opening whilst injectingthe compound into the grooves from the other end of the section.
 17. Amethod as claimed in 15, in which the setting or curing compound isinjected into the grooves of each further section by forming an openinginto the grooves from internally within the further section adjacent thepreviously-assembled section, and then drawing a vacuum from the groovesfrom the other end of the section whilst injecting the compound into thegrooves through said opening.
 18. A method as claimed in claim 16 orclaim 17, in which said compound is permitted to flow between theinterfacing edges of the respective segments.
 19. A method as claimed inany of claims 15 to 18, in which a further opening is formed frominternally within the further section into the pockets and a sealingagent is injected into those pockets through said further opening.
 20. Amethod as claimed in claim 19, in which said sealing agent comprises anon-setting mastic.
 21. A method of lining an existing closed duct,comprising effecting within the existing duct a pipe-construction methodas claimed in any of claims 8 to 19 so as to build-up the pipe in situin the duct but with clearance between the outer wall of the pipe andthe inner wall of the duct, and then filling said clearance with agrouting material.
 22. A method as claimed in any of claims 15 to 21,wherein a reinforcing strip is secured to at least one of the internaland external adjacent edge regions of two segments to bridge thelongitudinal joint.